Though I don't usually read business books, this one was fairly interesting. The thesis is that established, customer-focused companies are essentially helpless when confronted with a cheap, less-effective alternative. Because the interests of their customers force them to allocate resources towards maintaining and improving their current products, they can't muster the organizational will do develop and market lower-end products that don't meet their customers' needs. Christiansen points out a number of examples where these lower-end products repeatedly developed into larger markets and eventually displaced their higher-end competitors. The book was much longer than it needed to be, visiting and revisiting the same material many times, so I ended up skimming most of it.